1. Field of the Invention
The present invention relates to an optical system for use in a single-lens reflex camera, and more particularly, it pertains to a single-lens reflex camera optical system which includes a beam path splitter inside a photographing lens optical system, as in a motion picture camera and a compact single-lens reflex camera, so that a photographer can obtain through a view finder system a light split by the beam path splitter after having passed through a lens group located before the beam path splitter toward an object.
2. Description of the Prior Art
Until now for this type of single-lens reflex camera optical system, a photographing lens optical system, i.e., the most important element of a camera, is first designed to achieve the best corrected aberration to ensure high image forming performance on a film surface. A view finder system is then designed in consideration of aberration conditions of the lens group on the object side of a beam path splitter in the photographing lens optical system so that a favorable finder image can be obtained. As is widely known, however, a view finder system consists mainly of a combination of positive lens elements. This causes the view finder system itself to produce longitudinal aberration when the construction is simplified. Therefore, even if the lens group, located before the beam path splitter, is achromatized, longitudinal chromatic aberration occurs in a finder image on the focal plane. To obtain a favorable finder image accordingly, the longitudinal chromatic aberration must be corrected inside the view finder system, which, as a result, requires a specific number of elements for an achromatic lens, thus causing the entire optical system for a single-lens reflex camera to become a considerably complex lens construction.
U.S. Pat. No. 3,583,785 and U.S. Pat. No. 4,086,000 are cited of general interest.